Eco‐friendly vegetable leather dyeing using green and sustainable natural dye from Lannea schweinfurthii

Abstract Because of the hazardous effluent load of synthetic dyes, the global community is seeking the inclusion of natural dyes in various fields. Lannea schweinfurthii , widely cultivated in northern Tanzania, offers a promising natural dye source because its stem bark is rich in coloured phytochemicals. This study focused on extracting an organic dye from the stem bark of Lannea schweinfurthii using solvent extraction assisted by a magnetic stirrer and applying it to dye vegetable‐tanned leather. The influence of extraction temperature (40, 60, 80°C), time (10, 35, 60 minutes) and stem bark powder concentration (0.02, 0.06, 0.1 g/mL) were optimised using response surface methodology with a Box–Behnken Design. Under optimised conditions of 0.1 g/mL concentration, 43 minutes and 77°C, a maximum absorbance of 4.9 was achieved. At these conditions, the desirability function of 1.000, which indicates the optimal performance, was attained. Fourier Transform–infrared analysis confirmed the presence of flavonoids, phenols, tannins and their derivatives. Also, a zeta potential of −1.36 was recorded. The dyeing process was conducted with and without mordant. The premordanting technique was followed using 2% (on weight of leather) of potassium aluminium sulphate, copper sulphate and ferrous sulphate as mordants. The dyed samples exhibited various colour shades with good colour fastness, enhanced colour intensity and notable antimicrobial properties. Therefore, dyeing using the stem bark of Lannea schweinfurthii represents a major step toward the eco‐friendly fabrication of leather products.